1. Field
Example embodiments may relate to nonvolatile memory devices and/or methods of fabricating nonvolatile memory devices.
2. Description of the Related Art
Related art volatile memory devices, such as DRAMs, may have increased integration density, reduced power consumption, and/or a simplified, familiar manufacturing process, but related art volatile memory devices may lose stored data if power is turned off. Related art nonvolatile memory devices, such as flash memory devices, may have a high erasing voltage, lower integration density, and/or slower operation speed, but related art nonvolatile memory devices may maintain stored data even if power is turned off.
Related art nonvolatile memory devices such as FRAM, MRAM, PRAM, and RRAM have been developed and commercialized. In these related art nonvolatile memory devices, approximately the same integration density and operational characteristics of DRAMs may be obtained. Related art nonvolatile memory devices may be manufactured using related art semiconductor memory device manufacturing processes and may maintain stored data if power is turned off.
Storage nodes may be configured differently among a related art ferroelectric random access memory (FRAM), magnetic random access memory (MRAM), phase change random access memory (PRAM), and a resistance random access memory (RRAM).
A storage node of a FRAM may include an upper electrode, a lower electrode, and/or a ferroelectric. A storage node of an MRAM may include an upper magnetic layer, a lower magnetic layer, and/or a tunneling film therebetween. A magnetic polarization direction of one of the upper magnetic layer and the lower magnetic layer of the MRAM may be fixed in a given direction, and that of the other layer may be in the same or opposite direction. The other layer may be a free layer.
A PRAM may include an upper electrode, a lower electrode, a phase change layer between the upper and lower electrodes, and/or a contact that connects the lower electrode and the phase change layer.
An RRAM may include an upper metal layer, a lower metal layer, and/or an insulating layer (a resistance layer) therebetween.
Operational characteristics of related art nonvolatile memory devices may depend on current-voltage characteristics of a material layer in a storage node on which data may be recorded.
For example, in the insulating layer of a storage node of a RRAM, the resistance characteristics may change according to a voltage applied. Changed resistance characteristics may not further change until an erase voltage is applied, even if power is turned off.
RRAM may have a nonvolatile characteristic as described above, lower reproducibility, larger resistance deviations, and/or a more easily damaged upper electrode.